The present invention relates to a method and a system for preventing reverse rotation operation of an engine. More particularly, the present invention relates to a method for preventing reverse rotation operation of an engine in which a forward rotation and a reverse rotation of an engine are detected, and control is performed to prevent the reverse rotation of the engine such that damage to the same does not occur.
When starting from a stopped state on a hill, a vehicle often reverses slightly before moving forward. This may be caused by the delayed operation of the accelerator pedal by the driver (or slow depressing of the accelerator pedal and releasing of the clutch pedal in a vehicle with a manual transmission) upon brake release, or it may result naturally as a result of the weight of the vehicle. When this occurs, the engine rotates in a direction opposite from the normal direction, that is, the engine rotates in reverse.
However, since a distinction between forward and reverse rotation of the engine is not made by the logic employed in typical present-day microprocessors used in vehicles, the RPM gauge in a cluster operates during both forward and reverse engine rotation. Further, during the reverse rotation of the engine, the engine control unit makes erroneous determinations based on normal vehicle operating condition logic and performs control to effect fuel injection. The engine control unit also performs malfunction diagnosis during the reverse rotation of the engine such that erroneous determinations of malfunctions occur. As a result, warning lights are illuminated when no malfunction exists.
With the use of such conventional control, logic control is performed identically regardless of whether the engine is undergoing forward or reverse rotation. Therefore, when the engine is rotating reversibly, it is determined that the vehicle is operating normally and control logic is performed in the normal manner. As a result, fuel injection is performed and other abnormal operations are effected. In extreme cases, the vehicle is propelled in the reverse direction. Also, it may be erroneously determined that the vehicle is malfunctioning.
The present invention provides a method for preventing reverse rotation operation of an engine. Forward rotation and reverse rotation of an engine are detected, and control is performed to prevent abnormal operation and the mis-diagnosis of a malfunction during reverse rotation operation.
In a preferred embodiment of the present invention, a crank angle sensor (CAS), a cam position sensor (CPS), and an engine control unit receiving signals from the CAS and the CPS representative of the sensed parameters perform engine control according to a predetermined control program. The control program comprises determining if a piston in a specific cylinder is at a predetermined location using a level of the CPS signal at a leading edge and the trailing edge of the CAS signal, determining if the engine is rotating in reverse using the CPS signal level at the leading edge and trailing edge of the CAS signal in the case where it is determined that the piston of the specific cylinder is at the predetermined locations, and discontinuing operation of the engine if it is determined that the engine is undergoing reverse rotation.
Preferably, it is determined that the piston in the specific cylinder is at the predetermined position if the level of the CPS signal is at HIGH at both the leading edge and the trailing edge of the CAS signal. It is also preferable that the specific cylinder is a second cylinder and the predetermined position is top dead center.
The determining if the engine is rotating in reverse comprises detecting the level of the CPS signal at the leading edges and falling edges of the CAS signal after it is determined that the piston in the specific cylinder is at the predetermined position, storing the CPS signal levels as a binary number, in which a 1 is stored if the CPS signal level is HIGH and a 0 is stored if the CPS signal level is LOW, and determining that the engine is rotating in reverse if the stored binary number is identical to a predetermined number.
In another preferred embodiment of the present invention, a system for preventing reverse rotation operation of an engine comprises a crank angle sensor (CAS) for detecting a rotating angle of a crankshaft, a cam position sensor (CPS) for detecting a position of a camshaft, and an engine control unit receiving signals from the CAS and the CPS to perform engine control to prevent the reverse rotation operation of the engine. The engine control unit is programmed to perform control steps comprising determining if a piston in a specific cylinder is at a predetermined location using the level of the CPS signal at a leading edge and a trailing edge of the CAS signal, determining if the engine is rotating in reverse using the CPS signal level at the leading edge and trailing edge of the CAS signal in the case where it is determined that the piston of the specific cylinder is at the predetermined location, and discontinuing operation of the engine if it is determined that the engine is undergoing reverse rotation.